Rhythmic variations in behavior are displayed by many organisms, ranging from single cells to man. When the rhythm persists under constant conditions, and has a period of about one day, depending little on temperature, the rhythm is called “circadian” (Konopka, R. J. and Benzer, S. (1971) Proc. Nat. Acad. Sci. USA 68, 2112-2116).
Circadian rhythms are generated by endogenous biological pacemakers (circadian clocks) and are present in most living organisms including humans, fungi, insects and bacteria (Dunlap, J. C. (1999) Cell 96, 271-290; Hastings, J. W. et al. Circadian Rhythms, The Physiology of Biological Timing. In: Prosser, C. L. ed. Neural and Integrative Animal Physiology, New York: Wiley-Liss (1991) 435-546; Allada, R. et al. (1998) Cell 93, 791-804; Kondo et al. (1994) Science 266, 1233-1236; Crosthwaite, S. K. et al. (1997) Science 276, 763-769; Shearman, L. P. et al. (1997) Neuron, 19, 1261-1269). Circadian rhythms are self-sustaining and constant even under conditions of total darkness, but can be synchronized (entrained) to a new day/night regime by environmental signals such as light and temperature cycles (Pittendrigh, C. S. (1993) Annu. Rev. Physiol., 55, 16-54; Takahashi, J. S. (1995) Annu. Rev. Neurosci. 18, 531-553; Albrecht, U. et al. (1997) Cell, 91, 1055-1064). Circadian clocks are essential for maintaining biological rhythms and regulate a variety of circadian behaviors such as daily fluctuations in behavior, food intake and the sleep/wake cycle, as well as physiological changes such as hormone secretion and fluctuations in body temperature (Hastings, M. (1997) Trends Neurosci. 20, 459-464; Reppert, S. M. and Weaver, D. R. (1997) Cell 89, 487-490).
Genetic and molecular studies in the fruit fly Drosophila melanogaster led to elucidation of some of the genes involved in circadian rhythmicity. These studies led to recognition of a pathway that is closely auto-regulated and comprised of a transcription/translation-based negative feed back loop (Dunlap, J. C. (1999) Cell, 96, 271-290; Dunlap, J. C. (1996) Annu. Rev. Genet. 30, 579-601; Hall, J. C. (1996) Neuron, 17, 799-802). The core elements of the circadian oscillator in Drosophila consists of two stimulatory proteins dCLOCK/dBMAL (CYCLE) and two inhibitory proteins dPERIOD (dPER) and dTIMELESS (dTIM). dCLOCK and dBMAL heterodimerize forming the transcription factor dCLOCK/dBMAL that promotes expression of two genes termed Drosophila Period (dper) and Drosophila Timeless (dtim). Ultimately the mRNAs from these genes are transcribed to afford the proteins dPER and dTIM, respectively. For several hours the protein products dPER and dTIM are synthesized and phosphorylated in the cytoplasm, reach a critical level, and form heterodimers that are translocated into the nucleus. Once in the nucleus dPER and dTIM function as negative regulators of their own transcription, accumulation of dPER and dTIM declines, and activation of dper and dtim by dCLOCK/dBMAL starts again (Zylka, M. J. et al. (1998) Neuron 20, 1103-1110; Lowrey, P. L. et al. (2000) 288, 483-491). The dper gene has been shown to be a necessary element in controlling circadian rhythms in adult eclosion (the emergence of the adult fly from the pupa) behavior and locomotor activity (Konopka, R. J., & Benzer, S. (1971) Proc. Natl. Acad. Sci. USA, 68, 2112-2116). Missense mutations of the per gene can either shorten (perS) or lengthen (perL) the period of circadian rhythms, while nonsense mutations (pero) cause arrhythmicity in their behaviors (Hall, J. C. (1995) Trends Neurosci. 18, 230-240).
In mammals, the suprachiasmatic nuclei (SCN) of the anterior hypothalamus are the site of a master biological clock (for review see Panda et al, (2002) Nature 417, 329-335; Reppert, S. M. and Weaver, D. R. (1997) Cell, 89, 487-490). The SCN clock is entrained to the 24 hour day by the daily light-dark cycle, with light acting through both direct and indirect retina-to-SCN pathways (Klein, D. C. et al. (1991) Suprachiasmatic Nuclei: The Mind's Clock, Oxford University Press, New York). In the SCN of rodents, three Per genes have been identified and cloned, and are designated as mouse Per1 (mPer1), mPer2 and mPer3. The protein products of these mammalian genes (mPER1, mPER2, mPER3) share several regions of homology to each other, and each mammalian Per gene encodes a protein with a protein dimerization domain designated as PAS (PAS is an acronym for the first three proteins PER, ARNT and SIM found to share this functionally important dimerization domain) that is highly homologous to the PAS domain of insect PER. All Per messenger RNAs (mRNAs) and protein levels oscillate during the circadian day and are intimately involved in both positive and negative regulation of the biological clock, but only mPER1 and mPER2 oscillate in response to light (Zylka, M. J. et al. (1998) Neuron 20, 1103-1110; Albrecht, U. et al., (1997) Cell 91, 1055-1064; Shearman, L. P. et al. (1997) Neuron 19, 1261-1269). The mammalian homolog of the Drosophila tim gene was cloned and designated as mTim. However, there was no evidence for mPER-mTIM interactions analogous to those observed in Drosophila, and it was suggested that PER-PER interactions may have replaced the function of PER-TIM dimers in the molecular workings of the mammalian circadian clock (Zylka, M. J. et al., (1998) Neuron 21, 1115-1122). Another possibility is that rhythms in PER1 and PER2 form negative feedback loops that regulate the transcriptional activity of the Clock protein (via their PAS domains), which, in turn, drives expression of either or both Per genes (Shearman, L. P. et al. (1997) Neuron 19, 1261-1269).
Understanding the roles of the three mPer genes in the mammalian clockwork has been the subject of much investigation. The structural homology of the mPER proteins to dPER led to the expectation that the mPER proteins would function as negative elements in the mammalian feedback loop. PER1 is believed to be involved in the negative regulation of its own transcription in the feedback loop, but recent evidence points to it being involved in the input pathway (Hastings, M. H. et al. (1999) Proc. Natl. Acad. Sci. USA 26, 15211-15216). PER2 is the most well characterized protein, and mPER2 mutant mice (mPer2Brdm1), lacking 87 residues at the carboxyl portion of the PAS dimerization domain, have a shortened circadian cycle in normal light-dark settings, but show arrhythmicity in complete darkness. The mutation also diminishes the oscillating expression of both mPer1 and mPer2 in the SCN, indicating that mPer2 may regulate mPer1 in vivo (Zheng, B. et al. (1999) Nature 400, 169-173). PER2 has been shown to have a dual function in the regulation of the “gears” of the central clock (Shearman, L. P. et al. (2000) Science 288, 1013-1018). In that study, PER2 was shown to bind to cryptochrome (CRY) proteins and translocate to the nucleus where CRY negatively regulated transcription driven by the CLOCK and BMAL1 positive transcriptional complexes. Upon nuclear entry, PER2 initiated the positive arm of the clock by positively regulating BMAL1 transcription by a yet unidentified mechanism. The function of PER3 is poorly understood; however, in mPer3 knockout mice a subtle effect on circadian activity is observed, and therefore PER3 has been suggested to be involved in the circadian controlled output pathways (Shearman, L. P. et al. (2000) Mol. Cell. Biol. 17, 6269-6275). It has been reported that mPER proteins interact with each other and that mPER3 can serve as a carrier of mPER1 and mPER2 to bring them into the nucleus which is critical for the generation of circadian signals in the SCN (Kume, K. et al. (1999) Cell 98, 193-205; Takano, A. et al. (2000), FEBS Letters, 477, 106-112).
Phosphorylation of the components of the circadian clock has been postulated to regulate the duration of the cycle. The first genetic evidence that a specific protein kinase regulates the Drosophila circadian rhythm was the discovery of the novel gene doubletime (dbt), encoding a protein serine/threonine kinase (DBT) (Price J. L. et al. (1998) Cell 94, 83-95; Kloss B. et al. (1998) Cell 94, 97-107). Missense mutations in the dbt result in an altered circadian rhythm. Null alleles of dbt result in hypophosphorylation of dPER and arrhythmia.
The mammalian kinases most closely related to DBT are casein kinase Iε (CKIε) and casein kinase Iδ (CKIδ). Both kinases have been shown to bind to mPER1, and several studies have shown that CKIε phosphorylates both mouse and human PER1 (Price J. L. et al. (1998) Cell 94, 83-95; Kloss B. et al. (1998) Cell 94, 97-107). In a study with human embryonic kidney 293T cells co-transfected with wild-type hCKIε, hPER1 showed a significant increase in phosphorylation (evidenced by a shift in molecular mass). In this study, the phosphorylated hPER1 had a half-life of approximately twelve hours whereas unphosphorylated hPER1 remained stable in the cell for more that 24 hours, suggesting phosphorylation of hPER1 leads to a decrease in protein stability (Kessler, G. A. et al. (2000) NeuroReport, 11, 951-955). Another study also showed the consequence of PER1 phosphorylation by hCKIε includes both cytoplasmic retention and protein instability (Vielhaber, E. et al. (2000) Mol. Cell. Biol. 13, 4888-4899; Takano, A. et al. (2000) FEBS Letters 477, 106-112).
There has been no biochemical reason to choose between CKIε or CKIδ as a potential regulator in mammals until Lowery et al. [(2000) Science 288, 483-491] found that in the Syrian Golden hamster, semidominant mutations in CKIε (tau mutation, Ralph, M. R. and Menaker, M. (1988) Science 241, 1225-1227) caused a shortened circadian day in both heterozygous (22 h) and homozygous animals (20 h). In this instance, reduced levels of CKIε activity resulted in less PER phosphorylation with presumably higher levels of cytoplasmic PER protein leading to enhanced nuclear entry and altered circadian cycles. More recently, it has been suggested that CKIδ may also be involved in regulating circadian rhythmicity by post-translation modification of mammalian clock proteins hPER1 and hPER2 [Camacho, F. et al., (2001) FEBS Letters 489(2,3), 159-165]. Thus, inhibitors, including small molecule inhibitors, of mammalian or human CKIε and/or CKIδ provide a novel means to phase shift or reset the circadian clock. As discussed below, the alteration of circadian rhythm may find utility for the treatment of sleep or mood disorders.
U.S. Pat. No. 6,555,328 B1 discloses screening methods in cells to identify compounds that alter circadian rhythms based on a test compound altering the ability of human casein kinase 1ε and/or human casein kinase 1δ to phosphorylate the human clock proteins hPER1, hPER2 and hPER3. For example, HEK293T cells are co-transfected with hCKIε and Per1 or Per2. For the purpose of evaluating the relevancy of CKIε inhibition and CKIε inhibitors to circadian biology, a high-throughput cellular assay (33rd Annual Meeting, Soc. for Neurosci., Nov. 8-12, 2003, Abstract numbers 284.1, 284.2, and 284.3) was developed in which circadian rhythm could be monitored in a routine manner. The assay consists of Rat-1 fibroblasts stably expressing an Mper1-luc construct, thus enabling the determination of the rhythmic activation of the Mper1 promoter in living cells by repeatedly estimating luciferase activity by monitoring light-output over several days. The repeated measure format of the assay permits accurate and reproducible assessment of the concentration-dependent effects of CKIε inhibitors on circadian rhythm and provides the nexus for relating CKIε inhibition to circadian period alteration.
Sleep disorders have been classified into four major categories that include primary sleep disorders (dyssomnias and parasomnias), sleep disorders associated with medical/psychiatric disorders and a category of proposed sleep disorders for sleep disorders that cannot be classified due to insufficient data. Primary sleep disorders are thought to arise from abnormalities in the intrinsic systems responsible for sleep-wake generation (homeostatic system) or timing (circadian system). Dyssomnias are disorders in initiating or maintaining sleep and include primary insomnia, hypersomnia (excessive sleepiness), narcolepsy, breathing-related sleep disorder, circadian rhythm sleep disorder, and dyssomnias not otherwise specified. Primary insomnia is characterized by the persistence (>1 month) in difficulty of initiating and maintaining sleep or of non-restorative sleep. Difficulties in sleeping associated with primary insomnia leads to significant distress or impairment, including daytime irritability, loss of attention and concentration, fatigue and malaise, and deterioration of mood and motivation. Circadian rhythm sleep disorders include jet lag syndrome, shift work sleep disorder, advanced sleep phase syndrome and delayed sleep phase syndrome (J. Wagner, M. L. Wagner and W. A. Hening, Annals of Pharmacotherapy (1998) 32, 680-691). Individuals in a forced sleep paradigm demonstrate a greater wakefulness, as a percentage of sleep time, at certain periods of circadian day (Dijk and Lockley, J. Appl. Physiol. (2002) 92, 852-862). It has been generally accepted that with age there is an advance in our circadian rhythm for sleep and often results in less quality sleep (Am J Physiol Endocrinol Metab. (2002) 282, E297-E303). Thus, sleep occurring out of circadian phase may suffer in qualitative and quantitative terms, as further exemplified by alterations in sleep with shift work and jet lag. Disturbance of the human circadian clock can cause sleep disorders and agents that modulate circadian rhythmicity, such as an inhibitor of CKIε and/or CKIδ, may be useful for the treatment of sleep disorders, and particularly circadian rhythm sleep disorders.
Mood disorders are divided into depressive disorders (“unipolar depression”), bipolar disorders, and two disorders based on etiology that include mood disorder due to a general medical condition and substance-induced mood disorder. Depressive disorders are subclassified as major depressive disorder, dysthymic disorder and depressive disorder not otherwise specified. Bipolar disorders are subclassified as bipolar I disorder and bipolar II disorder. It has been observed that the specifier “seasonal pattern” can be applied to major depressive disorders that are recurrent and to the pattern of major depressive episodes in bipolar I disorder and bipolar II disorder. Prominent anergy, hypersomnia, overeating, weight gain, and a craving for carbohydrates often characterize major depressive episodes that occur in a seasonal pattern. It is unclear whether a seasonal pattern is more likely in major depressive disorder that is recurrent or in bipolar disorders. However, within the bipolar disorders, a seasonal pattern appears to be more likely in bipolar II disorder than in bipolar I disorder. In some individuals the onset of manic or hypomanic episodes may also be linked to a particular season. The winter-type seasonal pattern appears to vary with latitude, age and sex. Prevalence increases with higher latitudes, younger persons are at higher risk for winter depressive episodes, and females comprise 60% to 90% of persons with seasonal pattern. Seasonal affective disorder (SAD), a term commonly used in the literature, is a subtype of mood disorder that in the Diagnostic and Statistical Manual of Mental Disorders IV (DSM-IV) (American Psychiatric Association: “Diagnostic and Statistical Manual of Mental Disorders”, Fourth Edition, Text Revision. Washington, D.C., American Psychiatric Association, 2000) is denoted by the term “with seasonal pattern” when describing a seasonal pattern of major depressive episodes in bipolar I disorder, bipolar II disorder or recurrent major depressive disorder (E. M. Tam et al., Can. J. Psychiatry (1995) 40, 457-466). The characteristics and diagnoses of depressive disorders, major depressive disorder, major depressive episode, bipolar I disorder, bipolar II disorder and seasonal effects are described in DSM-IV,
Patients suffering from major depressive disorders, including SAD that is characterized by recurrent depressive episodes typically in winter, have been shown to be positively responsive to light therapy (Kripke, Journal of Affective Disorders (1998) 49(2), 109-117). The success of bright light treatment for patients with SAD and major depression resulted in the proposal of several hypotheses to explain the underlying mechanism of action for the therapeutic effect of light. These hypotheses included the “circadian rhythm hypothesis” that suggests the antidepressant effect of bright light could be associated with phase-shifting the circadian pacemaker relative to sleep (E. M. Tam et al., Can. J. Psychiatry (1995) 40, 457-466). In support of the link between light therapy and circadian rhythm, clinically effective light therapy in major depressive disorders causes a concomitant shift in circadian phase and the clinical effectiveness of light therapy appears to depend on the phase-shifting ability of the light therapy (Czeisler et al., The Journal of Physiology (2000) 526 (Part 3), 683-694; Terman et al., Arch. Gen. Psychiatry (2001) 58, 69-75). Additionally, light-therapy has been shown to accelerate and augment the effectiveness of the pharmacological treatment of major depressive disorders (Benedetti et al., J. Clin. Psychiatry (2003) 64, 648-653). Thus, inhibition of casein kinase Iε and/or casein kinase Iδ would be expected to cause a circadian phase shift and such inhibition represents a potential clinically effective mono- or combined therapy for mood disorders.
It should be noted that sleep disturbance is a criterion symptom for many psychiatric disorders (W. V. McCall, J. Clin. Psychiatry (2001) 62 (suppl 10), 27-32). Sleep disturbances are a common feature of depressive disorders and insomnia is the sleep disturbance that is frequently reported in depression, occurring in over 90% of depressed patients (M. E. Thase, J. Clin. Psychiatry (1999) 60 (suppl 17), 28-31). Accumulating evidence supports a common pathogenesis for primary insomnia and major depressive disorder. It has been hypothesized that corticotrophin releasing factor (CRF) hyperactivity (due to genetic predisposition or possibly early stress) and stress induce a process leading to exaggerated and protracted sleep disturbances, and eventually primary insomnia. Circadian rhythmicity in CRF secretion under nonstressed conditions may play a role in the normal sleep-wake expression (G. S. Richardson and T. Roth, J. Clin Psychiatry (2001) 62 (suppl 10), 39-45). Thus, agents that modulate circadian rhythmicity, for example by inhibition of casein kinase Iε and/or casein kinase Iδ, may be useful for treatment of depressive disorders due to effects on CRF secretion.
All of the references referred to hereinabove are incorporated herein by reference in their entirety.
Thus it is an object of this invention to provide methods of using 3-arylthioindole-2-carboxamides, 5-substituted-3-arylthioindole-2-carboxamides and related analogues as inhibitors of human casein kinase Iε phosphorylation of the human clock protein Period (hPER) which are therefore useful, as pharmaceutical agents, especially in the treatment and/or prevention of diseases and disorders associated with the central nervous system. This object and other objects of this invention become apparent from the detailed discussion of the invention that follows.